1. Field of the Invention
The present invention generally relates to semiconductor devices and, more particularly, to a semiconductor device used for a small fingerprint sensor and a manufacturing method of such a semiconductor device.
2. Description of the Related Art
In recent years, a fingerprint sensor, which enables personal verification by a fingerprint, has become widely used. Since the fingerprint sensor is used for small electronic equipments such as a portable terminal or a portable phone, there is a demand for reducing a mounting area of a semiconductor device for fingerprint sensors. Moreover, in order to recognize a fingerprint by contacting a finger directly to a semiconductor device in the fingerprint sensor, high-reliability in packaging is required for the semiconductor device for fingerprint sensors. Further, since the fingerprint sensor is used for consumer electronic equipments such as a potable terminal or a portable phone in many cases, cost reduction is required for the semiconductor device for fingerprint sensors.
A conventional semiconductor device for fingerprint sensors is formed as a semiconductor device, similar to semiconductor devices currently used for other applications, by combining and packaging a semiconductor element and an interposer (a redistribution wiring layer or a redistribution wiring substrate). However, in such a conventional packaging, a mounting area of the semiconductor device is larger than the semiconductor element since an interposer is used. Moreover, since assembly is performed on an individual chip basis and a test is performed on an individual semiconductor device basis, it is difficult to reduce an assembling and manufacturing cost.
FIG. 1 is a cross-sectional view of a conventional semiconductor device for fingerprint sensors. A semiconductor element 1 is mounted on an interposer 2, and is electrically connected to the interposer 2 by wires 3 such as bonding wires. The semiconductor element 1 is packaged by being encapsulated by a seal resin 4 in a state where a part of a surface of the semiconductor element 1, which part serves as a sensor surface 1b, is exposed. The interposer 2 is a multilayer wiring substrate, and solder balls 5, as external connection terminals, are formed on a side opposite to the surface where the semiconductor element 1 is mounted.
As shown in FIG. 2, the packaged semiconductor device for fingerprint sensors is mounted to an internal board 7 in an equipment using the solder balls 5. The internal board 7 on which the semiconductor device for fingerprint sensors is mounted is incorporated into a housing 6 of the equipment in a state where the surface of the element, which serves as the sensor surface 1b, is exposed to outside from an interior of the equipment.
The above-mentioned conventional semiconductor device for fingerprint sensors is disclosed in Japanese Laid-Open Patent Applications No. 2002-150256 and No. 2004-319678.
In the above-mentioned conventional semiconductor device for fingerprint sensors, the interposer 2 is used, and, thus, a connection part (portion for applying wire bonding) is required between the semiconductor element 1 and the interposer 2. Therefore, the area of the semiconductor device for fingerprint sensors is larger than the semiconductor element 1 by an area corresponding to the connection part, which hinders a reduction in the mounting area.
In assembly of the semiconductor device for fingerprint sensors, a connection with the interposer 2 is carried out for each semiconductor element 1. Also in a test as a semiconductor device, the test is carried out for each semiconductor device. Therefore, in manufacturing of the semiconductor device for fingerprint sensors, the assembly and the test process are carried out on an individual semiconductor element 1 basis. That is, the same process is carried out for the number of semiconductor elements 1, which results in low processing efficiency.
With respect to the reliability of mounting, external connection terminals such as the solder balls 5 are connected to an internal board when mounting the semiconductor device to the internal board. Since the solder ball connection of the semiconductor device is made to flat terminals of the interposer 2, the mounting strength is determined by the size of the connection area. In order to enlarge the connection area for the purpose of improving the mounting strength, the terminal area of the interposer 2 may be enlarged. However, increasing the terminal area may results in further increasing the area of the interposer 2 rather than decreasing the area of the interposer 2. That is, increasing the terminal area of the interposer 2 increases the area of the semiconductor device for fingerprint sensors, which hinders reduction of the mounting area.